The application of reproductive technologies varies widely in livestock production, especially in terms of its use in bovines. However, some particular breeds, such as the Lidia breed (fighting bull breed), present particular morphological traits, such as the smaller size, which pose challenges to the application of assisted reproductive techniques (ART) ( Gomez, 2006 ), such artificial insemination (AI) or embryo transfer (ET). Moreover, as Lidia breed animals are selected for aggressiveness ( Silva et al. , 2006 ), this behavioral trait may also be a complicating factor in ART procedures.

The anatomy of the female reproductive apparatus is one of the basic issues in some livestock cattle production operations. Most of the reproductive structures can be palpated through the rectum; this is the basis of routine fertility work performed through the application of ART, pregnancy diagnoses and clinical examinations ( Mukasa-Mugerwa, 1989 ; Jackson & Cockroft, 2002 ). The characteristics of the female bovine reproductive apparatus differs among subspecies, or even among breeds. Reports in old references, related to the reproductive apparatuses of Bos indicus ( Megale & Couto, 1959 ) and Bos taurus ( Perkins et al. , 1954 ; Roberts, 1971 ; Filho, 1982 ; Hafez, 1982; Sisson & Grossman, 1986 ), state that, in general, the reproductive tract of Bos indicus cattle is smaller than that of taurine cattle ( Mukasa-Mugerwa, 1989 ). Recent studies have evaluated specific characteristics of the reproductive apparatus of the female bovine, such as the ovaries in pregnant and non-pregnant Bos indicus cows ( Chacur et al. , 2006 ; Ramos et al. , 2008 ) and, more recently, Bardas et al. (2014) , characterized the female reproductive apparatus of the Baltata Româneasca breed ( Bos taurus ). As far as the Lidia bovine reproductive apparatus is concerned, only two reports described their small size and the nonexistence of uterine body (Goméz 2006; Patrón & Télles, 2013 ). Additionally, the number of Lidia cattle oocytes per ovary was low when compared to the recovery rates from other breeds ( Demyda-Peyrás et al. , 2013 ). The same authors connected this finding with the moderate fertility in Lidia breed ( Jiménez et al. , 2007 ). They also attributed it to the fact that their selection process is focused on aggressiveness because hostile animals have lower reproductive performances ( Phocas et al. , 2006 ), as previously described. Nevertheless, the lower oocytes recovery rates after slaughtering animals, observed by Demyda-Peyrás et al. (2013) cannot be directly related with reproductive performance impairment, but rather to the small size of Lidia ovaries.

The aim of the present study was characterize the Lidia cow reproductive apparatus through morphometric assessment, and compare the results with those obtained from the Holstein Friesian (HF) breed.

The Lidia cattle breed is constituted by several lineages, with different morphological traits ( Montesinos, 2002 ). This fact has been not confirmed by the present study as heifers belonging to Lidia cattle showed similar values for all parameters measured among Brava dos Açores and Domecq cows (Table 1), both lineages without genetic relationships ( Correia et al. , 2014 ). For almost traits, the reproductive apparatuses observed in Lidia heifers were smaller in size than heifers belonging to the HF breed (C, D and E). Compared to animals of about the same age both for Lidia and HF, Lidia cattle had a small vulvas and vaginas (length (L) = 27.31 ± 0.53 cm; width (W) = 2.07 ± 0.14 cm) compared to the HF group with 32.69 ± 0.64 and 3.39 ±, 0.20 respectively for length and width ( p ≤0.01). For the group of cows, values obtained by this parameter were higher (37.52 ± 0.71 cm), which supported previously published data ( Roberts, 1971 ; Filho, 1982 ; Sisson & Grossman, 1986 ; Hafez, 1988 ). In these previous studies, measurements varied between 30 cm and 42 cm. Results obtained in the present study for the measurements of this parameter in Lidia cattle, are however similar to those published by Bardas et al. (2014) , working with cows from the Baltata Româneasca breed, in which the vaginal length was 27.22 cm.

In the present study, differences were also observed between Lidia and HF cattle for the cervix measurements, being respectively L = 4.67 ± 0.17 cm; W = 1.42 ± 0.11 cm and L = 6.27 ± 0.30 cm; W = 1.85 ± 0.10 cm for Lidia and HF, as well as for its number of annular rings (5.1 ± 0.17 vs 3.33 ± 0.11) ( p ≤0.01). Jackson & Cockroft (2002) , analyzed heifers and reported that their cervix was about 2 cm in width and 4 cm in length. As far as the number of rings are concerned, our values for the HF ring numbers are not in agreement with those obtained by Roberts (1971) , in which the number of cervix rings for Bos taurus , excluding Lidia, was similar to those obtained for the Lidia heifers by the present study. Nevertheless, it must be noted that the measurement criteria described in several studies are not clear and, for this reason, comparisons with other reports must be used only cautiously.

No statistical differences were observed among breeds related to uterine body length. However, for width, Lidia heifers presented a much thinner uterine body than that observed in the HF heifers (1.40 ± 0.67 cm vs 3.16 ± 0.16 cm; p ≤0.01). For the uterine horns and ovary, data were collected separately for left and right horn and ovary. No statistical differences were found among them and, for this reason, data represent the average obtained for both. Lidia heifers showed lower lengths compared to the HF animals, with 12.24 ± 0.32 cm vs 19.07 ± 0.62 cm ( p ≤0.01), respectively. In terms of ovary size, no statistical differences were observed among heifers from different breeds. The only statistical difference was observed between the numbers of follicles, which was significantly higher in the HF as compared to the Lidia breed, respectively 11.00 ± 1.15 vs 23.97 ± 4.46. As the ovaries of Lidia cattle showed lower number of follicles when compared with HF animals, one would expect that the number of oocytes in Lidia ovaries is smaller, as suggested by Demyda-Peyrás et al. (2013) .

This experiment was the first to carry out a morphemic characterization of the female reproductive apparatus of Lidia breed bovines, using Brava dos Açores population and Domecq lineage as model, while also showing clear differences between Lidia and other cattle breeds, in this case the HF. The vulva and vagina, uterine body and the uterine horns of Lidia cattle showed lower sizes as compared with HF heifers from different ages, evidencing the small size of the Lidia heifer's reproductive apparatus with more than 30 months. The small uterine body and high number of cervix rings found in Lidia cattle is another uncommon trait, when compared with female bovines of other breeds. The results of this research provide useful information for understanding the reproductive approach to be used in the Lidia cattle breed.

IITAA is fully acknowledged. Ms. Meredith Cannella is fully acknowledged for her English correction and documentation of the manuscript. We also thanks to Instituto de Alimentação e Mercados Agrícolas (IAMA) and Mr. José Baldaya (Rego Botelho Lidia breeder).